The solubility of different alkanes in polyethylene (PE) of different densities, as well as the solubility of the polymers in the alkanes, and the degree of swelling of the powders were studied as a function of temperature. It was found that the solubility of linear low density polyethylene (LLDPE) was as much as 6 times greater than that of High Density Polyethylene (HDPE) at the same temperature, and that LLDPE swelled at least 50% more than HDPE the same diluent at the same temperature. The breakthrough curves also showed that lighter alkanes swell the PE more at a given temperature than do the heavier ones, and that the breakthrough points (the temperature at which the swelling vs temperature curves change slope) occur at lower temperatures for PE of lower density. Gel formation is observed for medium and low density polyethylenes in pentane and hexane. This quantitative information will be useful in developing process models for different industrial polymerization processes, as particle swelling can have a significant impact on slurry viscosity and the flow stability and solids loading of commercial reactors.